1. Technical Field
The embodiments herein generally relate to semiconductor processing, and, more particularly, to the removal of excess noble metal material during contact electrode processing.
2. Description of the Related Art
In conventional semiconductor processing systems, many dangerous chemicals are used simply because an alternative has not been found. For example, during contact electrode processing in a front end of line (FEOL) application, aqua regia is commonly used to remove unreacted platinum and platinum metal alloys (e.g., NiPt/Pt). Aqua regia is a mixture of nitric acid and hydrochloric acid, usually in a molar ratio of 1:3. Moreover, when used as a solvent, aqua regia typically forms shallow craters devoid of silicide in the Ni(Pt)Si film. Moreover, aqua regia is very corrosive and highly flammable.
These factors contribute to making aqua regia an undesirable compound for use in industrial processes. Aqua regia, however, is used in conventional systems because it is known to dissolve Pt and thereby resulting in soluble hexachloroplatinic acid. Ideally, aqua regia dissolves Pt because it is a mixture of nitric acid (HNO3) and hydrochloric acid (HCl). Since nitric acid is a powerful oxidizer, it will dissolves Pt to form platinum ions (Pt4+). Thereafter, the oxidized platinum ions react with chloride ions from the hydrochloric acid resulting in the chloroplatinate ion. Industrial use of aqua regia to dissolve Pt and form hexachloroplatinic acid, however, is far from ideal and leaves undesirable amounts of Pt and Pt residues during, for example, contact electrode processing in a FEOL application.
Therefore, what is needed is a composition and method that allows for the safe removal of advanced materials (e.g., platinum) during semiconductor processing and manufacturing.